1 /* Perform doloop optimizations
2 Copyright (C) 1999, 2000 Free Software Foundation, Inc.
3 Contributed by Michael P. Hayes (m.hayes@elec.canterbury.ac.nz)
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
28 #include "hard-reg-set.h"
29 #include "basic-block.h"
33 /* This module is used to modify loops with a determinable number of
34 iterations to use special low-overhead looping instructions.
36 It first validates whether the loop is well behaved and has a
37 determinable number of iterations (either at compile or run-time).
38 It then modifies the loop to use a low-overhead looping pattern as
41 1. A pseudo register is allocated as the loop iteration counter.
43 2. The number of loop iterations is calculated and is stored
46 3. At the end of the loop, the jump insn is replaced by the
47 doloop_end pattern. The compare must remain because it might be
48 used elsewhere. If the loop-variable or condition register are
49 used elsewhere, they will be eliminated by flow.
51 4. An optional doloop_begin pattern is inserted at the top of the
56 #ifdef HAVE_doloop_end
58 static rtx doloop_condition_get
60 static unsigned HOST_WIDE_INT doloop_iterations_max
61 PARAMS ((const struct loop_info
*, enum machine_mode
, int));
62 static int doloop_valid_p
63 PARAMS ((const struct loop
*, rtx
));
64 static int doloop_modify
65 PARAMS ((const struct loop
*, rtx
, rtx
, rtx
, rtx
, rtx
));
66 static int doloop_modify_runtime
67 PARAMS ((const struct loop
*, rtx
, rtx
, rtx
, enum machine_mode
, rtx
));
70 /* Return the loop termination condition for PATTERN or zero
71 if it is not a decrement and branch jump insn. */
73 doloop_condition_get (pattern
)
81 /* The canonical doloop pattern we expect is:
83 (parallel [(set (pc) (if_then_else (condition)
86 (set (reg) (plus (reg) (const_int -1)))
87 (additional clobbers and uses)])
89 Some machines (IA-64) make the decrement conditional on
90 the condition as well, so we don't bother verifying the
91 actual decrement. In summary, the branch must be the
92 first entry of the parallel (also required by jump.c),
93 and the second entry of the parallel must be a set of
94 the loop counter register. */
96 if (GET_CODE (pattern
) != PARALLEL
)
99 cmp
= XVECEXP (pattern
, 0, 0);
100 inc
= XVECEXP (pattern
, 0, 1);
102 /* Check for (set (reg) (something)). */
103 if (GET_CODE (inc
) != SET
|| ! REG_P (SET_DEST (inc
)))
106 /* Extract loop counter register. */
107 reg
= SET_DEST (inc
);
109 /* Check for (set (pc) (if_then_else (condition)
112 if (GET_CODE (cmp
) != SET
113 || SET_DEST (cmp
) != pc_rtx
114 || GET_CODE (SET_SRC (cmp
)) != IF_THEN_ELSE
115 || GET_CODE (XEXP (SET_SRC (cmp
), 1)) != LABEL_REF
116 || XEXP (SET_SRC (cmp
), 2) != pc_rtx
)
119 /* Extract loop termination condition. */
120 condition
= XEXP (SET_SRC (cmp
), 0);
122 if ((GET_CODE (condition
) != GE
&& GET_CODE (condition
) != NE
)
123 || GET_CODE (XEXP (condition
, 1)) != CONST_INT
)
126 if (XEXP (condition
, 0) == reg
)
129 if (GET_CODE (XEXP (condition
, 0)) == PLUS
130 && XEXP (XEXP (condition
, 0), 0) == reg
)
133 /* ??? If a machine uses a funny comparison, we could return a
134 canonicalised form here. */
140 /* Return an estimate of the maximum number of loop iterations for the
141 loop specified by LOOP or zero if the loop is not normal.
142 MODE is the mode of the iteration count and NONNEG is non-zero if
143 the the iteration count has been proved to be non-negative. */
144 static unsigned HOST_WIDE_INT
145 doloop_iterations_max (loop_info
, mode
, nonneg
)
146 const struct loop_info
*loop_info
;
147 enum machine_mode mode
;
150 unsigned HOST_WIDE_INT n_iterations_max
;
154 HOST_WIDE_INT abs_inc
;
158 abs_inc
= INTVAL (loop_info
->increment
);
167 code
= swap_condition (loop_info
->comparison_code
);
168 min_value
= loop_info
->final_equiv_value
;
169 max_value
= loop_info
->initial_equiv_value
;
173 code
= loop_info
->comparison_code
;
174 min_value
= loop_info
->initial_equiv_value
;
175 max_value
= loop_info
->final_equiv_value
;
178 /* Since the loop has a VTOP, we know that the initial test will be
179 true and thus the value of max_value should be greater than the
180 value of min_value. Thus the difference should always be positive
181 and the code must be LT, LE, LTU, LEU, or NE. Otherwise the loop is
182 not normal, e.g., `for (i = 0; i < 10; i--)'. */
188 unsigned HOST_WIDE_INT umax
;
189 unsigned HOST_WIDE_INT umin
;
191 if (GET_CODE (min_value
) == CONST_INT
)
192 umin
= INTVAL (min_value
);
196 if (GET_CODE (max_value
) == CONST_INT
)
197 umax
= INTVAL (max_value
);
199 umax
= ((unsigned)2 << (GET_MODE_BITSIZE (mode
) - 1)) - 1;
201 n_iterations_max
= umax
- umin
;
211 if (GET_CODE (min_value
) == CONST_INT
)
212 smin
= INTVAL (min_value
);
214 smin
= -((unsigned)1 << (GET_MODE_BITSIZE (mode
) - 1));
216 if (GET_CODE (max_value
) == CONST_INT
)
217 smax
= INTVAL (max_value
);
219 smax
= ((unsigned)1 << (GET_MODE_BITSIZE (mode
) - 1)) - 1;
221 n_iterations_max
= smax
- smin
;
226 if (GET_CODE (min_value
) == CONST_INT
227 && GET_CODE (max_value
) == CONST_INT
)
228 n_iterations_max
= INTVAL (max_value
) - INTVAL (min_value
);
230 /* We need to conservatively assume that we might have the maximum
231 number of iterations without any additional knowledge. */
232 n_iterations_max
= ((unsigned)2 << (GET_MODE_BITSIZE (mode
) - 1)) - 1;
239 n_iterations_max
/= abs_inc
;
241 /* If we know that the iteration count is non-negative then adjust
242 n_iterations_max if it is so large that it appears negative. */
244 && n_iterations_max
> ((unsigned)1 << (GET_MODE_BITSIZE (mode
) - 1)))
245 n_iterations_max
= ((unsigned)1 << (GET_MODE_BITSIZE (mode
) - 1)) - 1;
247 return n_iterations_max
;
251 /* Return non-zero if the loop specified by LOOP is suitable for
252 the use of special low-overhead looping instructions. */
254 doloop_valid_p (loop
, jump_insn
)
255 const struct loop
*loop
;
258 const struct loop_info
*loop_info
= LOOP_INFO (loop
);
260 /* The loop must have a conditional jump at the end. */
261 if (! any_condjump_p (jump_insn
)
262 || ! onlyjump_p (jump_insn
))
264 if (loop_dump_stream
)
265 fprintf (loop_dump_stream
,
266 "Doloop: Invalid jump at loop end.\n");
270 /* Give up if a loop has been completely unrolled. */
271 if (loop_info
->n_iterations
== loop_info
->unroll_number
)
273 if (loop_dump_stream
)
274 fprintf (loop_dump_stream
,
275 "Doloop: Loop completely unrolled.\n");
279 /* The loop must have a single exit target. A break or return
280 statement within a loop will generate multiple loop exits.
281 Another example of a loop that currently generates multiple exit
282 targets is for (i = 0; i < (foo ? 8 : 4); i++) { }. */
283 if (loop_info
->has_multiple_exit_targets
|| loop
->exit_count
)
285 if (loop_dump_stream
)
286 fprintf (loop_dump_stream
,
287 "Doloop: Loop has multiple exit targets.\n");
291 /* An indirect jump may jump out of the loop. */
292 if (loop_info
->has_indirect_jump
)
294 if (loop_dump_stream
)
295 fprintf (loop_dump_stream
,
296 "Doloop: Indirect jump in function.\n");
300 /* A called function may clobber any special registers required for
301 low-overhead looping. */
302 if (loop_info
->has_call
)
304 if (loop_dump_stream
)
305 fprintf (loop_dump_stream
,
306 "Doloop: Function call in loop.\n");
310 /* Some targets (eg, PPC) use the count register for branch on table
311 instructions. ??? This should be a target specific check. */
312 if (loop_info
->has_tablejump
)
314 if (loop_dump_stream
)
315 fprintf (loop_dump_stream
,
316 "Doloop: Computed branch in the loop.\n");
320 if (! loop_info
->increment
)
322 if (loop_dump_stream
)
323 fprintf (loop_dump_stream
,
324 "Doloop: Could not determine iteration info.\n");
328 if (GET_CODE (loop_info
->increment
) != CONST_INT
)
330 if (loop_dump_stream
)
331 fprintf (loop_dump_stream
,
332 "Doloop: Increment not an integer constant.\n");
336 /* There is no guarantee that a NE loop will terminate if the
337 absolute increment is not unity. ??? We could compute this
338 condition at run-time and have a additional jump around the loop
339 to ensure an infinite loop. */
340 if (loop_info
->comparison_code
== NE
341 && INTVAL (loop_info
->increment
) != -1
342 && INTVAL (loop_info
->increment
) != 1)
344 if (loop_dump_stream
)
345 fprintf (loop_dump_stream
,
346 "Doloop: NE loop with non-unity increment.\n");
350 /* Check for loops that may not terminate under special conditions. */
351 if (! loop_info
->n_iterations
352 && ((loop_info
->comparison_code
== LEU
353 && INTVAL (loop_info
->increment
) > 0)
354 || (loop_info
->comparison_code
== GEU
355 && INTVAL (loop_info
->increment
) < 0)))
357 /* If the comparison is LEU and the comparison value is UINT_MAX
358 then the loop will not terminate. Similarly, if the
359 comparison code is GEU and the initial value is 0, the loop
362 Note that with LE and GE, the loop behaviour can be
363 implementation dependent if an overflow occurs, say between
364 INT_MAX and INT_MAX + 1. We thus don't have to worry about
367 ??? We could compute these conditions at run-time and have a
368 additional jump around the loop to ensure an infinite loop.
369 However, it is very unlikely that this is the intended
370 behaviour of the loop and checking for these rare boundary
371 conditions would pessimize all other code. */
372 if (loop_dump_stream
)
373 fprintf (loop_dump_stream
,
374 "Doloop: Possible infinite iteration case ignored.\n");
381 /* Modify the loop to use the low-overhead looping insn where LOOP
382 describes the loop, ITERATIONS is an RTX containing the desired
383 number of loop iterations, ITERATIONS_MAX is a CONST_INT specifying
384 the maximum number of loop iterations, and DOLOOP_INSN is the
385 low-overhead looping insn to emit at the end of the loop. This
386 returns non-zero if it was successful. */
388 doloop_modify (loop
, iterations
, iterations_max
,
389 doloop_seq
, start_label
, condition
)
390 const struct loop
*loop
;
404 jump_insn
= prev_nonnote_insn (loop
->end
);
406 if (loop_dump_stream
)
408 fprintf (loop_dump_stream
, "Doloop: Inserting doloop pattern (");
409 if (GET_CODE (iterations
) == CONST_INT
)
410 fprintf (loop_dump_stream
, HOST_WIDE_INT_PRINT_DEC
,
411 INTVAL (iterations
));
413 fputs ("runtime", loop_dump_stream
);
414 fputs (" iterations).", loop_dump_stream
);
417 /* Emit the label that will delimit the top of the loop.
418 This has to be done before the delete_insn call below, to prevent
419 delete_insn from deleting too much. */
420 emit_label_after (start_label
, loop
->top
? loop
->top
: loop
->start
);
421 LABEL_NUSES (start_label
)++;
423 /* Discard original jump to continue loop. The original compare
424 result may still be live, so it cannot be discarded explicitly. */
425 delete_insn (jump_insn
);
427 counter_reg
= XEXP (condition
, 0);
428 if (GET_CODE (counter_reg
) == PLUS
)
429 counter_reg
= XEXP (counter_reg
, 0);
435 switch (GET_CODE (condition
))
438 /* Currently only NE tests against zero and one are supported. */
439 if (XEXP (condition
, 1) == const0_rtx
)
441 else if (XEXP (condition
, 1) != const1_rtx
)
446 /* Currently only GE tests against zero are supported. */
447 if (XEXP (condition
, 1) != const0_rtx
)
450 /* The iteration count needs decrementing for a GE test. */
453 /* Determine if the iteration counter will be non-negative.
454 Note that the maximum value loaded is iterations_max - 1. */
455 if ((unsigned HOST_WIDE_INT
) INTVAL (iterations_max
)
456 <= ((unsigned)1 << (GET_MODE_BITSIZE (GET_MODE (counter_reg
)) - 1)))
460 /* Abort if an invalid doloop pattern has been generated. */
467 if (GET_CODE (count
) == CONST_INT
)
468 count
= GEN_INT (INTVAL (count
) - 1);
470 count
= expand_binop (GET_MODE (counter_reg
), sub_optab
,
472 0, 0, OPTAB_LIB_WIDEN
);
475 /* Insert initialization of the count register into the loop header. */
476 convert_move (counter_reg
, count
, 1);
477 sequence
= gen_sequence ();
479 emit_insn_before (sequence
, loop
->start
);
481 /* Some targets (eg, C4x) need to initialize special looping
483 #ifdef HAVE_doloop_begin
487 init
= gen_doloop_begin (counter_reg
,
488 GET_CODE (iterations
) == CONST_INT
489 ? iterations
: const0_rtx
, iterations_max
,
490 GEN_INT (loop
->level
));
495 sequence
= gen_sequence ();
497 emit_insn_after (sequence
, loop
->start
);
502 /* Insert the new low-overhead looping insn. */
503 emit_jump_insn_before (doloop_seq
, loop
->end
);
504 jump_insn
= prev_nonnote_insn (loop
->end
);
505 JUMP_LABEL (jump_insn
) = start_label
;
507 /* Add a REG_NONNEG note if the actual or estimated maximum number
508 of iterations is non-negative. */
511 REG_NOTES (jump_insn
)
512 = gen_rtx_EXPR_LIST (REG_NONNEG
, NULL_RTX
, REG_NOTES (jump_insn
));
518 /* Handle the more complex case, where the bounds are not known at
519 compile time. In this case we generate a run_time calculation of
520 the number of iterations. We rely on the existence of a run-time
521 guard to ensure that the loop executes at least once, i.e.,
522 initial_value obeys the loop comparison condition. If a guard is
523 not present, we emit one. The loop to modify is described by LOOP.
524 ITERATIONS_MAX is a CONST_INT specifying the estimated maximum
525 number of loop iterations. DOLOOP_INSN is the low-overhead looping
526 insn to insert. Returns non-zero if loop successfully modified. */
528 doloop_modify_runtime (loop
, iterations_max
,
529 doloop_seq
, start_label
, mode
, condition
)
530 const struct loop
*loop
;
534 enum machine_mode mode
;
537 const struct loop_info
*loop_info
= LOOP_INFO (loop
);
538 HOST_WIDE_INT abs_inc
;
547 enum rtx_code comparison_code
;
549 increment
= loop_info
->increment
;
550 initial_value
= loop_info
->initial_value
;
551 final_value
= loop_info
->final_value
;
554 abs_inc
= INTVAL (increment
);
561 comparison_code
= loop_info
->comparison_code
;
562 unsigned_p
= (comparison_code
== LTU
563 || comparison_code
== LEU
564 || comparison_code
== GTU
565 || comparison_code
== GEU
566 || comparison_code
== NE
);
568 /* The number of iterations (prior to any loop unrolling) is given by:
569 (abs (final - initial) + abs_inc - 1) / abs_inc.
571 However, it is possible for the summation to overflow, and a
574 abs (final - initial) / abs_inc + (abs (final - initial) % abs_inc) != 0
576 If the loop has been unrolled, then the loop body has been
577 preconditioned to iterate a multiple of unroll_number times.
578 The number of iterations of the loop body is simply:
579 abs (final - initial) / (abs_inc * unroll_number).
581 The division and modulo operations can be avoided by requiring
582 that the increment is a power of 2 (precondition_loop_p enforces
583 this requirement). Nevertheless, the RTX_COSTS should be checked
584 to see if a fast divmod is available. */
587 /* abs (final - initial) */
588 diff
= expand_binop (mode
, sub_optab
,
589 copy_rtx (neg_inc
? initial_value
: final_value
),
590 copy_rtx (neg_inc
? final_value
: initial_value
),
591 NULL_RTX
, unsigned_p
, OPTAB_LIB_WIDEN
);
593 if (loop_info
->unroll_number
== 1)
601 shift_count
= exact_log2 (abs_inc
);
605 /* abs (final - initial) / abs_inc */
606 iterations
= expand_binop (GET_MODE (diff
), lshr_optab
,
607 diff
, GEN_INT (shift_count
),
611 /* abs (final - initial) % abs_inc */
612 extra
= expand_binop (GET_MODE (iterations
), and_optab
,
613 diff
, GEN_INT (abs_inc
- 1),
617 /* If (abs (final - initial) % abs_inc == 0) jump past
618 following increment instruction. */
619 label
= gen_label_rtx();
620 emit_cmp_and_jump_insns (extra
, const0_rtx
, EQ
, NULL_RTX
,
621 GET_MODE (extra
), 0, 0, label
);
622 JUMP_LABEL (get_last_insn ()) = label
;
623 LABEL_NUSES (label
)++;
625 /* Increment the iteration count by one. */
626 iterations
= expand_binop (GET_MODE (iterations
), add_optab
,
627 iterations
, GEN_INT (1),
640 /* precondition_loop_p has preconditioned the loop so that the
641 iteration count of the loop body is always a power of 2.
642 Since we won't get an overflow calculating the loop count,
643 the code we emit is simpler. */
644 shift_count
= exact_log2 (loop_info
->unroll_number
* abs_inc
);
648 iterations
= expand_binop (GET_MODE (diff
), lshr_optab
,
649 diff
, GEN_INT (shift_count
),
655 /* If there is a NOTE_INSN_LOOP_VTOP, we have a `for' or `while'
656 style loop, with a loop exit test at the start. Thus, we can
657 assume that the loop condition was true when the loop was
660 `do-while' loops require special treatment since the exit test is
661 not executed before the start of the loop. We need to determine
662 if the loop will terminate after the first pass and to limit the
663 iteration count to one if necessary. */
668 if (loop_dump_stream
)
669 fprintf (loop_dump_stream
, "Doloop: Do-while loop.\n");
671 /* A `do-while' loop must iterate at least once. If the
672 iteration count is bogus, we set the iteration count to 1.
673 Note that if the loop has been unrolled, then the loop body
674 is guaranteed to execute at least once. */
675 if (loop_info
->unroll_number
== 1)
677 /* Emit insns to test if the loop will immediately
678 terminate and to set the iteration count to 1 if true. */
679 label
= gen_label_rtx();
680 emit_cmp_and_jump_insns (copy_rtx (initial_value
),
681 copy_rtx (loop_info
->comparison_value
),
682 comparison_code
, NULL_RTX
, mode
, 0, 0,
684 JUMP_LABEL (get_last_insn ()) = label
;
685 LABEL_NUSES (label
)++;
686 emit_move_insn (iterations
, const1_rtx
);
691 sequence
= gen_sequence ();
693 emit_insn_before (sequence
, loop
->start
);
695 return doloop_modify (loop
, iterations
, iterations_max
, doloop_seq
,
696 start_label
, condition
);
700 /* This is the main entry point. Process loop described by LOOP
701 validating that the loop is suitable for conversion to use a low
702 overhead looping instruction, replacing the jump insn where
703 suitable. We distinguish between loops with compile-time bounds
704 and those with run-time bounds. Information from LOOP is used to
705 compute the number of iterations and to determine whether the loop
706 is a candidate for this optimization. Returns non-zero if loop
707 successfully modified. */
709 doloop_optimize (loop
)
710 const struct loop
*loop
;
712 struct loop_info
*loop_info
= LOOP_INFO (loop
);
717 enum machine_mode mode
;
718 unsigned HOST_WIDE_INT n_iterations
;
719 unsigned HOST_WIDE_INT n_iterations_max
;
720 rtx doloop_seq
, doloop_pat
, doloop_reg
;
726 if (loop_dump_stream
)
727 fprintf (loop_dump_stream
,
728 "Doloop: Processing loop %d, enclosed levels %d.\n",
729 loop
->num
, loop
->level
);
731 jump_insn
= prev_nonnote_insn (loop
->end
);
733 /* Check that loop is a candidate for a low-overhead looping insn. */
734 if (! doloop_valid_p (loop
, jump_insn
))
737 /* Determine if the loop can be safely, and profitably,
738 preconditioned. While we don't precondition the loop in a loop
739 unrolling sense, this test ensures that the loop is well behaved
740 and that the increment is a constant integer. */
741 if (! precondition_loop_p (loop
, &initial_value
, &final_value
,
744 if (loop_dump_stream
)
745 fprintf (loop_dump_stream
,
746 "Doloop: Cannot precondition loop.\n");
750 /* Determine or estimate the maximum number of loop iterations. */
751 n_iterations
= loop_info
->n_iterations
;
754 /* This is the simple case where the initial and final loop
755 values are constants. */
756 n_iterations_max
= n_iterations
;
760 int nonneg
= find_reg_note (jump_insn
, REG_NONNEG
, 0) != 0;
762 /* This is the harder case where the initial and final loop
763 values may not be constants. */
764 n_iterations_max
= doloop_iterations_max (loop_info
, mode
, nonneg
);
766 if (! n_iterations_max
)
768 /* We have something like `for (i = 0; i < 10; i--)'. */
769 if (loop_dump_stream
)
770 fprintf (loop_dump_stream
,
771 "Doloop: Not normal loop.\n");
776 /* Account for loop unrolling in the iteration count. This will
777 have no effect if loop_iterations could not determine the number
779 n_iterations
/= loop_info
->unroll_number
;
780 n_iterations_max
/= loop_info
->unroll_number
;
782 if (n_iterations
&& n_iterations
< 3)
784 if (loop_dump_stream
)
785 fprintf (loop_dump_stream
,
786 "Doloop: Too few iterations (%ld) to be profitable.\n",
787 (long int) n_iterations
);
791 iterations
= GEN_INT (n_iterations
);
792 iterations_max
= GEN_INT (n_iterations_max
);
794 /* Generate looping insn. If the pattern FAILs then give up trying
795 to modify the loop since there is some aspect the back-end does
797 start_label
= gen_label_rtx ();
798 doloop_reg
= gen_reg_rtx (mode
);
799 doloop_seq
= gen_doloop_end (doloop_reg
, iterations
, iterations_max
,
800 GEN_INT (loop
->level
), start_label
);
801 if (! doloop_seq
&& mode
!= word_mode
)
803 PUT_MODE (doloop_reg
, word_mode
);
804 doloop_seq
= gen_doloop_end (doloop_reg
, iterations
, iterations_max
,
805 GEN_INT (loop
->level
), start_label
);
809 if (loop_dump_stream
)
810 fprintf (loop_dump_stream
,
811 "Doloop: Target unwilling to use doloop pattern!\n");
815 /* A raw define_insn may yield a plain pattern. If a sequence
816 was involved, the last must be the jump instruction. */
817 if (GET_CODE (doloop_seq
) == SEQUENCE
)
819 doloop_pat
= XVECEXP (doloop_seq
, 0, XVECLEN (doloop_seq
, 0) - 1);
820 if (GET_CODE (doloop_pat
) == JUMP_INSN
)
821 doloop_pat
= PATTERN (doloop_pat
);
823 doloop_pat
= NULL_RTX
;
826 doloop_pat
= doloop_seq
;
829 || ! (condition
= doloop_condition_get (doloop_pat
)))
831 if (loop_dump_stream
)
832 fprintf (loop_dump_stream
,
833 "Doloop: Unrecognizable doloop pattern!\n");
837 if (n_iterations
!= 0)
838 /* Handle the simpler case, where we know the iteration count at
840 return doloop_modify (loop
, iterations
, iterations_max
, doloop_seq
,
841 start_label
, condition
);
843 /* Handle the harder case, where we must add additional runtime tests. */
844 return doloop_modify_runtime (loop
, iterations_max
, doloop_seq
,
845 start_label
, mode
, condition
);
848 #endif /* HAVE_doloop_end */